Please help me.

1.The value of -8/15 x 20/64 is _____.
a. -1/6
b. 1/6
c. -2/3
d. 2/3

2. Find -8 ÷ -1/2.
a. 1/16
b. 16
c. -1/4
d. -4

3. Find -3/7 ÷ -1 1/14.
a. 2/5
b. 2 1/2
c. -2/5
d. 45/98

4. Estimate -12 4/9 x 5 7/8.
a. 72
b. -72
c. 78
d. -78

thanks for help?